Gabriela did 23 fewer push-ups than Tiffany in the morning. Tiffany did 30 push-ups. How many push-ups did Gabriela do?
Answer: Tiffany did 30 push-ups, and Gabriela did 23 fewer than that, so find the difference. The difference is $30 - 23$ push-ups. She did $30 - 23 = 7$ push-ups.